Brett Cannon added the comment:
As brought up on the PR, it turns out Path.absolute() is extremely under-tested.
Perhaps we should deprecate Path.absolute() instead of document it and properly test it (and the testing will be necessary to move forward with the documentation)? Path.resolve() handles absolute paths already while also resolving '.' and '..': https://docs.python.org/3/library/pathlib.html#pathlib.Path.resolve. It also works with non-existent paths so unless there's some performance issue I'm not aware of for resolving '.' and '..', then I say we deprecate Path.absolute().